Explanation
Bedrock is the solid, hard rock layer beneath soil and loose surface materials, forming the Earth's crust. It is not the upper soil layer, middle mantle, or a mountain feature. Thus, "The solid rock of the earth" is correct.
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Bedrock is the solid, hard rock layer beneath soil and loose surface materials, forming the Earth's crust. It is not the upper soil layer, middle mantle, or a mountain feature. Thus, "The solid rock of the earth" is correct.